The weight of a liquid varies directly with its volume. A liquid that weighs 12 kg has volume of 3 litres. What will be the weight of a liquid that has volume 4 litres?

Correct option is B

Given:

​Weight varies directly with volume

Weight = 12 kg when Volume = 3 litres

Required: Weight when Volume = 4 litres

Concept Used:

For direct variation, the relation is:

​$$\text{Weight} \propto \text{Volume} \Rightarrow \frac{W_1}{V_1} = \frac{W_2}{V_2}$$ 

Solution:

​$$\frac{12}{3} = \frac{W}{4} \Rightarrow 4 \times \frac{12}{3} = W$$​​

​$$W = 4 \times 4 = 16 \text{ kg}$$

Alternate Solution:

Weight of the liquid = W

Volume the liquid = V
ATQ,
W ∝ KV
12 ∝ K × 3
K ∝ 4
Now,
W ∝ 4 × 4
= 16